The present application is based on and claims priority from Japanese Patent Applications Hei 11-89790 filed Mar. 30, 1999, and Hei 11-224502 filed Aug. 6, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method and an apparatus for welding a plurality of windings of a rotary electric machine, which is preferable to be applied to a method and an apparatus for welding stator winding of a vehicle AC generator.
2. Description of the Related Art
It is well known that stator winding are welded together in the heat of arc discharges between an electrode and connection ends of the stator winding.
Because a magnet wire of the stator winding is usually covered with an insulation coating, it is necessary to protect the insulation coating from such welding heat. For this purpose, arc-voltage is intermittently applied to a limited portion each time so that the welding heat may not affect portions other than connection ends.
However, such an intermittent welding or a step of applying intermittent voltage to each limited portion may be affected by unstable welding current at the starting time of the arc welding, resulting in unstable levels of welding quality. Since such unstable welding current may cause an excessive heat condition, it is difficult to protect the insulation coating. Such an intermittent welding also necessitates many man-hours.
The present invention has been made to solve the above described problems, and, therefore, a main object of the invention is to protect insulation coatings of a stator winding.
Another object of the present invention is to provide a high-speed-and-stable welding method and welding apparatus.
According to a main aspect of the invention, a method comprising a step of inserting a protection member into each space between adjacent two of a plurality of connection ends, a step of activating a welder tool, and a step of moving the welder tool relative to the connection ends in the circumferential direction.
Because of the protection member inserted in the space between adjacent two of the connection ends, heat deterioration of the insulation coating between two of the connection ends can be prevented. The heat applied to one of the connection ends is conducted to another so that the connection ends just welded can be gradually cooled. Accordingly, blow holes or cracks formed at the connection ends can be suppressed. Because the connection ends just before being welded can be preheated, efficient welding can be achieved.
According to another aspect of the invention, the step of activating the welder tool and the step of moving the welder tool are alternately carried out.
Accordingly, the welder tool is activated to weld the connection ends. The connection ends and the welder tool are relatively moved in the circumferential direction so that the connection ends can be welded one by one. Because the portion between adjacent two of the connection ends is protected by the protecting member, the insulation coating of portions other than the connection ends can be prevented from deteriorating. The adjacent connection ends to have been welded before or to be welded next can be gradually cooled or heated.
According to another aspect of the invention, the step of activating and the step of moving are concurrently carried out. The activation of the welder tool and the moving of the same are carried out concurrently. In other words, the relative position between the connection ends and the welder tool is moved while the welder tool is activated. The welder tool is activated while it is moved between adjacent two of the connection ends. Because the protection member is disposed between adjacent two of the connection ends, deterioration of the insulation coating of portions other than the connection ends can be suppressed. In an arc-welding, because an arc voltage is continuously applied across the connection ends and a welder tool to activate the welder tool, the problem caused by unstable welding current at the starting time of the arc welding can be solved. Since the welder tool can be moved while the arc voltage is applied, the connection ends can be welded at a high speed.
According to another aspect of the invention, the protection member has an axial contact length L in contact with the copper segments, and the length L is equal to or larger than circumferential thickness T of the copper segment. Accordingly, the deterioration length of the insulation coating that corresponds to the length L can be reduced.
According to another aspect of the invention, a difference A between two copper segments is as thin as or thinner than ⅓ of a width W of said copper segment in circumferential direction.
Accordingly, the height H of the connection ends can be reduced so that the deterioration width W of the insulation coating can be reduced.
According to another main aspect of the invention, an apparatus of welding a plurality of connection ends of copper segments of a circumferentially disposed stator winding of a rotary electric machine comprises a welder tool movable relative to connection ends, a welder power source for activating the welder tool, moving means for moving the welder tool relative to connection ends, and protecting members inserted into each space between adjacent two of said plurality of connection ends.
The moving means can either move the welder tool or move the connection ends.